ApplicationSet tutorial

This topic walks you through creating a GitOps ApplicationSet in Harness.

Prerequisites

To set up an ApplicationSet, you'll need the following:

• Create a Harness GitOps agent to create the ApplicationSet.
• Create 2 target GitOps clusters. Dev and prod are used to deploy the child applications.
• GitHub account. You will be cloning the Argo Project's ApplicationSet repo and using one of its examples.
• Create a Harness GitOps repository with the Argo Project's ApplicationSet repo. We will be using one of its examples.

Step 1: Updating manifests in Git

The following example uses a Git generator and is in Argo project’s public repository.

1. Clone the repo and update git-generator-files.yaml with the following YAML keys/values and then save the changes.

   apiVersion: argoproj.io/v1alpha1  
   kind: ApplicationSet  
   metadata:  
     name: guestbook  
   spec:  
     generators:  
       - git:  
           repoURL: https://github.com/<YOUR_ACCOUNT_NAME>/applicationset.git  
           revision: HEAD  
           files:  
           - path: "examples/git-generator-files-discovery/cluster-config/**/config.json"  
     template:  
       metadata:  
         name: '{{cluster.name}}-guestbook'
         labels: 
           harness.io/envRef: '{{envTag}}'
           harness.io/serviceRef: '{{serviceTag}}'
           harness.io/buildRef: '{{releaseTag}}'
       spec:  
         project: <PROJECT_ID_IN_AGENT_PAGE>  
         source:  
           repoURL: https://github.com/<your account name>/applicationset.git  
           targetRevision: HEAD  
           path: "examples/git-generator-files-discovery/apps/guestbook"  
         destination:  
           server: '{{cluster.address}}'  
           namespace: default  
         syncPolicy:  
           automated: {}

   To get the project Id, go to GitOps Agents and find the Argo Project Id you want to use to create the ApplicationSet.

   

2. Navigate to applicationset/examples/git-generator-files-discovery/cluster-config/engineering/dev/config.json.

3. Replace "address": "https://1.2.3.4" with the Endpoint IP address for the dev target cluster. Ensure that you use the https:// scheme. Note that this cluster must be created beforehand.

4. Repeat step 2 for the prod target cluster by modifying the file applicationset/examples/git-generator-files-discovery/cluster-config/engineering/prod/config.json

Here is an example:

note

Both JSON and YAML formats are supported for ApplicationSets.

Step 2: Creating the ApplicationSet app

1. Similar to how you create a regular application in Harness GitOps, select Applications, and then select New Application.

2. Enter a name, choose the agent, leave the default Sync Policy settings, and select Continue.

3. In Source, enter the following settings and then select Continue.

   1. Repository URL: select the GitOps repository you added earlier.
   2. Target Revision: select master.
   3. Path: enter examples/git-generator-files-discovery.

   

4. In Destination, select the cluster and namespace in which the GitOps agent is installed.

Step 3: Sync the ApplicationSet app

You can sync from 2 places: Application view or PR pipeline. For syncing via the PR pipeline, please refer to Sync GitOps applications.

From the Application view, you can sync the Harness ApplicationSet application or the individual Applications independently.

If you configure automatic syncing in the ApplicationSet template, then the applications are synced automatically. See syncPolicy.automated in the following example.

  template:  
    metadata:  
      name: '{{cluster.name}}-guestbook'  
    spec:  
      project: 191b68fc  
      source:  
        repoURL: https://github.com/johndoe/applicationset.git  
        targetRevision: HEAD  
        path: "examples/git-generator-files-discovery/apps/guestbook"  
      destination:  
        server: '{{cluster.address}}'  
        namespace: default  
      syncPolicy:  
        automated: {}